Genome reveals why poop wouldn’t hurt a fly

"Anything that comes out of an animal, such as bacteria and viruses, house flies can take from that waste and deposit on your sandwich," says Jeff Scott. "House flies are the movers of any disgusting pathogenic microorganism you can think of." (Credit: Michael Hrabar/Flickr)

If you spend most of your time in dung piles and garbage heaps, you better have robust immune genes.

Scientists sequenced the genome of the house fly for the first time and found an expanded number of immune response and defense genes.

The findings could explain how flies quickly adapt to resist insecticides, which in turn could lead to new ways to control them.

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Adult house flies (Musca domestica) carry and transmit more than 100 human and animal diseases, including salmonellosis, anthrax, typhoid fever, tuberculosis, cholera, and diarrhea as well as parasites such as pinworms, roundworms, hookworms, and tapeworms.

House fly larvae are important animal waste decomposers and live in close contact with many animal pathogens.

“Anything that comes out of an animal, such as bacteria and viruses, house flies can take from that waste and deposit on your sandwich,” says Jeff Scott, professor of entomology at Cornell University and lead author of a paper published in the journal Genome Biology.

“House flies are the movers of any disgusting pathogenic microorganism you can think of.”

The genome, roughly twice the size of the fruit fly’s genome, revealed an expanded number of immune response and defense genes. The researchers also discovered an expansion in the number of cytochrome P450s, which help the flies metabolize environmental toxins.

Genetic ‘phone numbers’

“House flies have a lot more of these enzymes than would be expected based on other insects they are related to,” Scott says.

For example, the house fly’s close relative, the tsetse fly (Glossina morsitans), has half as many cytochrome P450s. These enzymes are more ancient than insecticides. “We don’t have a clear handle on why house flies need so many,” Scott says.

The M. domestica genome also revealed many genes for chemoreceptors, which detect certain chemical stimuli in the environment. These receptors are important in sensing food and moving in ways critical for survival, allowing house flies to detect a wide variety of different things, Scott says.

“If you think of the genome like a phone book, we now have the phone number of every gene. We now can study every gene. For any scientific question, we have a highway to get us there.”

One of those questions will focus on controlling house flies and developing new toxins that disrupt the fly’s internal balance by poisoning them or using RNAi to turn off specific genes and killing them.

Other researchers from Cornell and from Washington University in St. Louis and Auburn University are coauthors of the study. The National Institutes of Health and Cornell University Agricultural Experiment Station funded the work.